Automatic sandblast machine

ABSTRACT

An air driven sandblast machine comprising a storage means for the sand, a storage pot with an automatic filling device which operates to fill the storage means on the stopping of the machine and a selective air driven shaker system which may be alternatively usable in slurry blasting. The device further includes a muffler system to reduce noise. The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

United States Patent [191 Johnson et al.

[54] AUTOMATIC SANDBLAST MACHINE 3,034,263 5/1962 McDaniel 51/12 3,056,236 10/1962 McMillin 51/12 X [76] Inventors: Cllfford Johnson, 1536 Roberta Dr., 3,557,498 H1971 Lindsay I I i i I I I I I n 5H8 San Mateo, Mart!" 2,409,722 10/1946 Stark 51/8 Duncan, 15846 Via Del Sol, San Lorenzo 94580; Lauerance Primary ExaminerDnald G. Kelly Sannes, 625 Canyon Dr., Pacifica, Atwmey R S Sciascia et al all of Calif. 94044 1 1 [22]- Filed: June 23, 1972 I ABSTRACT [21] Appl' 265882 An air driven sandblast machine comprising a storage means for the sand, a storage pot with an automatic [52] U.S. Cl. 5l/l2 fillingdevice which operates to fill the storage means [51] Int. Cl. B24c 7/00 on the stopping of the machine and a selective air [58] Field of Search 51/8, 12 driven shaker system which may be alternatively usable in slurry blasting. The device further includes a [56] References Cited muffler system to reduce noise.

UNITED STATES PATENTS The invention described herein may be manufactured 3,543,444 12/1970 Mehta 51/12x and used by or for the Government of the United 3,073,070 1/1963 Mead 51/12 X States of America for governmental purposes without 3,521,407 7/1970 Nalley 51112 the payment of any royalties thereon or therefor. 3,427,749 2/1969 Ryan 51/12 3,148,484 9/1964 Meek 51/12 10 Claims, 11 Drawing Figures BRA/47 67m 52 B SANDBLAST 8 I8 HOSE 99 IOO 7 4/ 1 AUTOMATIC SANDBLAST MACHINE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates generally to an automatic sandblast machine, and more particularly, to an air driven automatic sandblast machine which has an automatic filling device that operates on the stopping of the machine and an air driven shaker system to control the flow of sand. l i

2. Description of the Prior Art Theold method of blasting used a semiautomatic electrical blasting machine. The old blasting devices had electric air inlet valves and an electric outlet valve. The sand was regulated by an electric vibrator unit located in a chamber within the machine and directly below the supply and sand storage chamber. Some of the disadvantages of this aforementioned system were as follows: the automatic controls were electrical in op eration, therefore unable to withstand the extreme loads and critical conditions required; the sand flow could not be preset and controlled at the machine; the machine had to be refilled by hand rather than by automatic operation; the electrical components were subject to failure due to the dust problems; and the exhaust from the old machines created a noise problem.

SUMMARY OF THE INVENTION Briefly, the present invention is an air driven sandblast machine comprising a storage means for the sand, a storage pot with an automatic filling device which operates to fill the storage means on the stopping of the machine and a selective pneumatically operated vibration unit alternatively usable in slurry blasting. The device further includes a muffler system to reduce noise.

The unique blasting machine overcomes the aforementioned problems in that it is completely automatic and operates under pneumatic principles that are essentially trouble free. The machine eliminates noise problems by the use of a muffling exhaust system. Moreover, the unique machine automatically fills itself whenever the operator shuts off the machine, thus eliminating the need for the operator to leave the work area to refill the system.

STATEMENTS OF THE OBJECTS OF INVENTION A primary object of the present invention is to provide a sandblast machine which will automatically refill itself upon turning off the machine.

Another object of the present invention is to provide a sandblast machine that is pneumatic and completely automatic in operation.

Another object of the present invention is to provide an essentially maintenance free sandblast machine.

Another object of the present invention is to provide a sandblast machine which reduces noise pollution.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation view of the sandblast machine;

FIG. 2 is a front elevation view of the mounting stand used to mount and support the sandblast machine of FIG. 1;

FIG. 3 is a front elevation view of the hopper used in conjunction with the sandblast machine of FIG. 1 and mounted on the upper platform of the mounting stand of FIG. 2;

FIG. 4 is a front elevation view of the sand transfer housing and associated components of the sandblast machine illustrated in FIG. 1;

FIG. 4A is a sectional view of the sand transfer hous- I ing and the housing associated components taken along lines 4A 4A of FIG. 4;

FIG. 5 is a front elevation view of the shaker housing,

parts broken away, used with the sandblast machine of FIG. 1;

' FIG. 5A is a section view of the shaker housing with its associated components, taken along lines 5A- 5A of FIG. 5; 7

FIG. 6 is a sideelevation view of the sandblast machine showing the accompanying piping arrangement with the upper portion being broken away for clarity;

- FIG. 7 is a rear elevation view of the sandblast machine showing its piping and controls;

FIG. 8 is a plan view of the feather touch control valve, which couples to the piping of the sandblast machine of FIG. 7, to control the sandblast machine illustrated in FIGS. 1 and 7; and

FIG. 9 is a side elevation view of the feather touch control illustrated in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the sandblast machine 9 comprises a sealing unit 13, a storage means 15, a vibrator unit 17, a sand transfer or automatic filling device 19 and mounting brackets 21a and 21b. The storage means 15 is a'cylinder 15b with a domed shaped top 15a and a cone shaped bottom 15c and designed to hold about 800 pounds of sand. Top 15a of storage means 15 is a convex shaped dome which opens onto and is attached to the automatic filling device 19 by sealing unit 13. The bottom of storage means 15 is cone shaped and tapers into an aperture which is attached to a hollow pipe coupling 18. Pipe coupling 18 attaches the vibrator unit 17 to the bottom 150 of storage means 15. This allows the sand to flow down from storage means 15 into the interior of vibrator unit 17.

Referring to FIGS. 1 and 2, mounting stand 23 includes mounting brackets 25 and 27 which are designed so that the face of mounting brackets 21a and 21b of sandblast machine 9 can be attached to the face of mounting brackets 25 and 27 by any standard well known methods such as securing by bolting or by weld- Referring to FIGS. 1 and 3, sand hopper 29 includes vent pipe 31, transfer gate 33 with sliding hatch 33a and extension skirt 35 with a rubber sleeve 37. The sand transfer device 19 includes a sand transfer housing 39, which connects to extension skirt 35 of sand hopper 29. The rubber sleeve 37 fits around sand guide 49 and attaches to extension skirt 35 of sand hopper 29 to prevent sand spillage around .the sand transfer device 19 and sand hopper 29 contacting points. The transfer gate 33 has a slidable hatch 33a that allows the sand in hopper 29 to flow into the storage means 15 when hatch 33a is in the open position. The sand hopper 29 is constructed to fit on the upper support platform 23a of the mounting sand 23, illustrated in FIG. 2.

Referring to FIGS. 1, 4 and 4A, the sand transfer housing 39 comprises flange 41, cylindrical shell 43, clearing pipes 45 and 46, cone 47, sand deflector ring 52, sand guide 49, cover plate 51, braces 55a and 55b, and screen 61. At the top 15a of storage means 15, shown in FIG. 1, is flange 40 in which the sealing unit 13 is located. Bolted to flange 41 is sand deflector ring 52 of sand transfer housing 39. Located at the top of sand transfer housing 39 is a screen 61 which is welded to the top of sand guide 49. The screen 61 is 22-mesh, or the like, and prevents any foreign material from entering machine 9. Sand guide 49 extends into the interior of sand transfer housing 39 and is attached to cone 47 by tubular support braces 55a and 55b. The tubular support braces 55a and 55b allow sand guide 49 to be vertically spaced somewhat above cone 47 so that the sand flowing down through sand guide 49 may be directed down and around cone 47. Located directly below deflector ring 52 and part of the transfer housing 39 walls are three equally spaced cutout apertures 57, 58, 59 which are cut out of the walls of the transfer housing 39. Apertures 57, 58, 59 are covered by a dust prevention mesh screen material or the like. These apertures allow ambient air to vent into the interior of the transfer housing 39. A cover plate 51 extends over the screened apertures 57, 58, 59. The cover plate 51 allows air to escape from sand transfer housing 39, but does not allow water to accumulate in housing 39. In actual operation, the sand flows from open sand hopper 29 through sand guide 49 and is diverted and directed over the exterior surface of cone 47 into the storage means 15. If the sand is wet, it can be blown clear in the sand transfer housing by blowing air through the clearing pipes 45, 46 which are attached to the sand transfer housing 39.

Installed in machine 9 is a sealing unit 13 which is illustrated in FIGS. 1 and 6. The sealing unit 13 comprises a half-domed shaped stopper 63, O-shaped sealing ring 65 and a retainer 67 which is attached to the top 15a of storage means 15 by flange 40. Installed over airline 72 in machine 9 is the stopper 63. When no air is flowing through airline 72, stopper 63 is in the down or open position. When machine 9 is pressurized air flows through line 72 causing stopper 63 to move up very rapidly to seal itself against seal 65.

Referring again to FIGS. 1, 4, 6, and 7, at the top 15a of storage means 15 is flange 42 to which the sealing unit 13 is attached. Bolted to flange 42 is sand transfer housing 39. At the top portion of sand transfer housing 39 is screen 61 which is welded to sandguide 49 to help prevent any foreign material from entering the machine 9. The sand guide 49, as described above, extends into housing 39. The sand deflector ring 52 is located directly below the cone 47 so that when the sand flows down around cone 47 it is directed along around and through the aperture of deflector ring 52.

Referring to FIGS. 1, 5, A, 6, and 7, attached to the bottom c of storage means 15 is the vibrator unit 17 which is coupled to bottom 150 by coupling 18. The vibrator unit 17 includes a shaker housing 71 and a vibrator device 127. The vibrator device 127 comprises hollow chamber 107, air inlet 101, and air outlet unit 103 and ball B and bolt 105 which extends down through the center of hollow chamber 107. The vibrator device 127 is used to regulate the flow of sand to the sandblasting hose 99, illustrated in FIG. 6. The shaker housing 71 is a small tank-shaped device which retains the vibrator 127 in place. The ball-shaped vibrator 127 is movably attached to plate 91 and pivotal spacer plate 91b by bolt 124. Plate 123 is rigidly secured to plate 91 by spacer plate 91a. Bolt 124 with spacer plate 9112 allows vibratory movement back and forth in a plane parallel to the lateral axis of housing 71 with bolt 124 acting as the pivot point for vibrator 127. Limit stops may be used to limit the lateral or vibratory movement of vibrator 127 along the lateral axis of housing 71. However, it has been found that the internal connections of elbows 125 and 126 to hoses 130 and 131, which are attached to ports 100 and 104, sufficiently limit the lateral movement of vibrator 127 without any excess loading on the components. The housing 71 further comprises head 93, nippled aperture 95, which attaches to coupling 18, cone 83, and short hollow nipple 83a. Short nipple 83a is attached to attaching joint 74 by normally open valve 74a, as illustrated in FIG. 6. Valve 74a can be opened or closed manually. A door frame 85 is attached and secured to plate 117 by standard weld nuts and gaskets. A movable access door 85a may be included to gain access to the interior of housing 71 through the opening 102 in frame 85 and center position of plate 117. The ball vibrator 127 has a hollow chamber 107 with a small ball B located in the hollow chamber 107 and further includes two hollow street elbows 125 and 126. Ball vibrator 127 is further attached to fixed plates 91 and 123 by bolt 124. Fixed plate 123 directs the flow of sand from the sand storage means 15 around the outer surface of vibrator 127. The bottom of the tank or shaker housing tapers sharply into a small nippled aperture 83a. The top of shaker housing 71 is a convex-shaped head 93, the center of which includes nippled aperture 95. Aperture 95 is joined to the bottom 15c of storage means 15 by coupling 18. The shaker housing 71 for the vibrator 127 has an air inlet port 100, which is attached to air supply line 84, and an air outlet port 104, which opens onto the ambient air. The ball vibrator 127 also has an air inlet 101 and an air outlet 103 which attach to hollow elbows 125 and 126. Attached to elbows 125 and 126 are rubber hoses 130, 131 with spring inserts 129 to keep the hoses 130, 131 from collapsing. Hoses 130, 131 are attached to air inlet ports and air outlet ports and 104, respectively. Air outlet 103 is attached to elbow 126 through hose 131 and is vented to the atmosphere through air outlet port 104. When air is allowed to flow through supply line 84, the vibrator 127 vibrates along a plane parallel to the lateral axis of housing 71. The actual vibration is caused by the small interior ball B interrupting the continuity of the entry and exit air flow within the hollow chamber 107 of the vibrator 127. The vibrator 127 should be properly sealed to prevent air pressure from escaping into the interior of housing 71. When vibrator 127 is operative, the sand stored in storage means 15 flows through the aperture 95 and is distributed on the upper exterior surface of fixed plate 123. The upper exterior surface of fixed plate 123 acts as a transient storage surface for the sand. The vibratory movement of vibrator 127 causes the stored sand on plate 123 to spill off plate 123 and flow down into aperture 83a where air under pressure from airline 70 directs the mixed sand and air through the hose attaching joint 74 and subsequently into the attached standard sandblast hose 99.

Referring to FIGS. 1, 5, 5A, 6, and 7, air supply line 70, which is attached to shaker housing 71 at hose attachingjoint 74, includes a swing check'valve 195 that keeps the sand-air mixture from surging back into air supply line 70. Between shaker housing 71 and hose attaching joint 74 is valve 74a which can be used to manually control the sand flow, if vibrator 127 has to be removed. Air hose 84 extends from regulator 81 to air inlet or fitting 100 which is attached to door frame 85 of shaker housing 71. Hose 84 supplies air to the ball vibrator 127 so that when the machine 9 is operative the speed of the vibrator can be regulated to control sand flow by the feather touch control 219, illustrated in FIG. 8. Machine 9 further includes self-cleaning sandtraps 251 and 253 connected to the air inlet side of valve 203 through valves 207A and 207B, respectively, and to air lines 255 and 257. When machine 9 is operative, air flows through lines 255 and 257 via vlave 203 to traps 251 and 253. The sandtraps 251 and 253 will function as one-way blow-back'valves to blow the residual sand left in the traps 251 and 253 back through the attached exhaust pipe 166 and into storage means of machine 9. 7

Referring to FIGS. 1, 5, 5A, 6, 7, 8, and 9, the operation and control of airflow to machine 9 is controlled by airline cables 213, 215 and 217 which are attached to feather touch control 219 and correspond to control cables 213, 215 and 217 of FIGS. 7, 8 and 9. The feather touch control 219, shown in FIGS. 8 and 9, is a standard control unit that has been modified to include third airline 217 to power vibrator 127. A description of the control unit is deemed unnecessary since it is a standard unit well known in the art. Cable 215 is connected to the continuous air pressure side of air inlet side of valve 203. The other end of cable 215 connects to the air inlet side of the feather touch control 219. The air flows through airline 198 and is directed to the air inlet side of valve 203 through to the inlet side of the feather touch control 219. When feather touch control lever 220 is depressed the air passes through the feather touch control 219 and into inlet valve 203. At the outlet side of feather touch control 219 is tee 179. One side of tee 179 has a /s-inch needle valve 178. Attached to needle valve 178 is control cable 217. The opposite end of control cable 217 attaches to air regulator 81. Adjustment of the Vs-inch needle valve 178 on air cable 217 increases or decreases air pressureon the diaphragm of regulator 81 which controls the amount of air flowing into ball vibrator 127. This in turn regulates the amount of vibration of ball B of ball vibrator 127 which controls the distribution of sand to the sandblast nozzle 99.

The side of the tee 179 opposite cable 217 is connected to a cable 213. Cable 213 extends tothe top of air valve 203. When the feather touch control lever 220 is depressed, air flows simultaneously through the airline 213 and the airline 217 to air valve 203 and regulator 81, respectively. I

Air continues to flow into tees 180 and 181 and on up to exhaust valves 207A. and 2078. The'line joining tees 180, 181 also allows air under pressure to flow through to regulator 82. This pressure closes both normally open valves 207A and 207B allowing pressure to build up in sandblast machine 9. When the feather touch lever 220 is released, air to regulators 81 and 82 is shut off stopping the ball vibrator 127 and also shutting off the air to both exhaust valves 207A and 2078 and mufflers 169A and 169B which muffle the exhaust air to the atmosphere. The exhaust pipe 166 inside blast machine 9 has a baffle 165, running along top of the machine 9 to below the exhaust inlet of exhaust pipe 166 which prevents the exhausting of sand in machine 9. When the air flow through airline 72 is shut off, stopper 63 falls, allowing sand to flow into the machine 9 from the automatic filling device 19. By regulating the air pressure on the diaphragm of regulator 81 by needle valve 178 at the feather touch control 219, the sandflow can be regulated to the proper amount for the job. By opening or closing needle valve 178, sand can be increased or decreased or even shut off completely.

Referring to FIGS. 1, 6 and 7, the air system for automatic blaster 9 begins at water tank air inlet 155. Water may be drained from the water tank 153 by valve 157 at the bottom of the tank 153. Air passes from air inlet 155 through the water tank 153 to the air filter 199. Air is supplied to inlet 155 by a standard air compressor. Directly after air filter 199, air line 198 extends and attaches to the normally closed air inlet valve 203. Airline 198 has a tee section 231 which attaches to tee 177. Airline 198 simultaneously supplies compressed air to. air hose 84 and pipe via tee section 231. Tee 177 attaches to valve 209. Hose 232 is attached to valve 209 and extends into a Y which then diverges into two individual hoses and 111 which connect to sand clearing pipes 45 and 46, respecitvely.

The other side of tee 177 is attached to the diaphragm of regulator 82. The diaphragm of regulator 82 is pressurized from hose 88 which extends from the top of regulator 82 through tee which is attached to the end of valve 203 through tee hose 181. When the machine 9 is in the static or nonoperative condition, there is normally air pressure in the airline from air inlet 155 to valve 203 to prevent surging.

Referring to FIGS. 1, 6, and 7, the attached pipe at the air outlet side of valve 203 makes a 90 turn towards the storage means 15 of blasting machine 9 to form a tee 69. Pipe line 72 off tee 69 extends into the storage means 15 and turns 90 upward within the interior portion of storage means 15. Pipe 72 extends through circular collar 20. The stopper 63 is positioned over line 72 so that when machine 9 is operative the air flow through line 72 moves stopper 63 upward to seal stopper 63 against seal 65. Simultaneous with the above described operation, air also passes through tee 69 and into pipe 70 through valve and into attaching joint 74. The air flowing through attaching joint 74 mixes with the metered sand flowing down from the shaker housing 71. The vibrator 127 with plate 123, which are located in shaker housing 71, meters the amount of sand flowing from storage means 15. The upper surface of plate 123 acts as a transient storage postion for the sand while also preventing large amounts of sand from accumulating at the bottom of shaker housing 71. When vibrator 127 is operative, the sand stored on the upper surface of plate 123 is vibrated off the surface and flows into attaching joint 74 to mix with the incoming air from hose 84. The mixture of air and sand is then carried to the blasting hose nozzle via the attaching joint 74 which attaches to a standard sandblast hose 99.

Pipe 259 with sand flow valve 260 can be used for rapid emptying of storage means 15 whenever this function is desired or required. Moreover, it should be noted that the size or shape of machine 9 is not critical as a factor in its operation, but in the manner and sequences in which machine 9 operates.

What is claimed is:

1. An automatic sandblast machine comprising in combination:

a. a means for replenishing the sand;

b. a means for storing said sand;

c. an automatic sand filling means located between said sand replenishing means and said sand storing means;

]. a means for activating and deactivating said sandblast machine;

e. a vibration means for supplying said sand to a sand applying means; and

f. said activating and deactivating means being operatively connected to said filling means and said vibration means by a controlling means wherein said sand filling means is activated to fill said storing means from said replenishing means when said activating and deactivating means is deactivated.

2. The device recited in claim 1 wherein said activating and deactivating means is a pneumatic activating and deactivating means which simultaneously activates and deactivates said filling means and said vibration means.

3. The device recited in claim 1 wherein said sand filling means is a pressure actuated valve with a valve sealing means, said filling means being located between said replenishing means and a sand storing means wherein said valve seals against said sealing means when said activating and deactivating means is actuated to close off the flow of the sand from said replenishing means simultaneously with the activation of said vibration means.

4. The device recited in claim 3 wherein said activating and deactivating means further comprises a pneumatic outlet valve and an air supply means located in said storing means and in operative contact with said actuated valve wherein said activating and deactivating means supply pneumatic pressure to said outlet valve through an air supply means to close said actuated valve when said activating and deactivating means is actuated.

5. The device recited in claim 4 wherein said actuated valve is positioned to return to the open position when said activating and deactivating means is deactivated. I

6. The device recited in claim 5 wherein said actuated valve comprises a sealing unit and a dome-shaped valve, said dome-shaped valve being positioned so that said valve is in the open position when the sandblast machine is not pressurized and said valve is in the closed position when said machine is pressurized.

7. The device recited in claim 3 wherein said vibration means is a shaker device comprising a housing and a ball vibrator mechanism located in said housing, said housing further including a pressure means to activate said vibration means simultaneously with said activating valve.

8. The device recited in claim 7 wherein said housing further includes an air inlet and an air outlet located on either side and attached to said ball vibrator mechanism wherein the air from said air inlet activates said vibrator mechanism.

9. The device recited in claim 8 wherein the sand flow flowing around said ball vibrator mechanism is metered by the amount of air flow within said air inlet and the amount of flow of air within said air outlet, said air flow propelling a ball within said ball vibrator mechanism, said ball disturbing the air flow within said ball vibrator mechanism causing said ball vibrator mechanism to vibrate the flow of sand over the exterior of said vibrator within said housing.

10. The device recited in claim 3 wherein said sand storing means further includes a muffling means connected between said activating and deactivating means and said vibrating means by an air conducting means to reduce the noise of the air flow. 

1. An automatic sandblast machine comprising in combination: a. a means for replenishing the sand; b. a means for storing said sand; c. an automatic sand filling means located between said sand replenishing means and said sand storing means; d. a means for activating and deactivating said sandblast machine; e. a vibration means for supplying said sand to a sand applying means; and f. said activating and deactivating means being operatively connected to said filling means and said vibration means by a controlling means wherein said sand filling means is activated to fill said storing means from said replenishing means when said activating and deactivating means is deactivated.
 2. The device recited in claim 1 wherein said activating and deactivating means is a pneumatic activating and deactivating means which simultaneously activates and deactivates said filling means and said vibration means.
 3. The device recited in claim 1 wherein said sand filling means is a pressure actuated valve with a valve sealing means, said filling means being located between said replenishing means and a sand storing means wherein said valve seals against said sealing means when said activating and deactivating means is actuated to close off the flow of the sand from said replenishing means simultaneously with the activation of said vibration means.
 4. The device recited in claim 3 wherein said activating and deactivating means further comprises a pneumatic outlet valve and an air supply means located in said storing means and in operative contact with said actuated valve wherein said activating and deactivating means supply pneumatic pressure to said outlet valve through an air supply means to close said actuated valve when said activating and deactivating meanS is actuated.
 5. The device recited in claim 4 wherein said actuated valve is positioned to return to the open position when said activating and deactivating means is deactivated.
 6. The device recited in claim 5 wherein said actuated valve comprises a sealing unit and a dome-shaped valve, said dome-shaped valve being positioned so that said valve is in the open position when the sandblast machine is not pressurized and said valve is in the closed position when said machine is pressurized.
 7. The device recited in claim 3 wherein said vibration means is a shaker device comprising a housing and a ball vibrator mechanism located in said housing, said housing further including a pressure means to activate said vibration means simultaneously with said activating valve.
 8. The device recited in claim 7 wherein said housing further includes an air inlet and an air outlet located on either side and attached to said ball vibrator mechanism wherein the air from said air inlet activates said vibrator mechanism.
 9. The device recited in claim 8 wherein the sand flow flowing around said ball vibrator mechanism is metered by the amount of air flow within said air inlet and the amount of flow of air within said air outlet, said air flow propelling a ball within said ball vibrator mechanism, said ball disturbing the air flow within said ball vibrator mechanism causing said ball vibrator mechanism to vibrate the flow of sand over the exterior of said vibrator within said housing.
 10. The device recited in claim 3 wherein said sand storing means further includes a muffling means connected between said activating and deactivating means and said vibrating means by an air conducting means to reduce the noise of the air flow. 